Field of the Invention
The present invention relates to a vibration isolation apparatus, a method of isolating vibration, a lithography apparatus that includes the vibration isolation apparatus disposed therein, and a method of producing a device.
Description of the Related Art
In apparatuses that perform precision measurement such as lithography apparatuses for manufacturing a semiconductor, atomic force microscopes, and scanning electron microscopes, measurement errors may be caused by receiving external vibration such as floor vibration. In order to address this, vibration isolation is required for these apparatuses so as to minimize transmission of external vibration to the apparatuses.
In a known related-art vibration isolation apparatus for precision measurement, an object is supported by an air spring, the natural frequency of which is smaller than that of a metal spring and which can suppress vibration of a large frequency band width. Examples of the vibration isolation apparatus featuring improved vibration isolation performance include a vibration isolation apparatus described in Japanese Patent Laid-Open No. 2009-47282. In this vibration isolation apparatus, by applying a force in the same direction as a direction in which an object is displaced, the natural frequency of a support system is reduced, and accordingly, the vibration isolation performance is improved.
Japanese Patent Laid-Open No. 2009-47282 describes a method of applying the force in the same direction as the direction of displacement of the object. In this method, the natural frequency is reduced by applying a force, which is calculated by multiplying displacement of an object by a fixed negative constant (−K). However, as patterns drawn by lithography apparatuses for manufacturing a semiconductor become miniaturized, further reduction of the natural frequency is required for vibration isolation apparatus.